Abstract
The detection of a gold nanoparticle contrast agent is demonstrated using a photothermal modulation technique and phase sensitive optical coherence tomography (OCT). A focused beam from a laser diode at 808 nm is modulated at frequencies of 500 Hz-60 kHz while irradiating a solution containing nanoshells. Because the nanoshells are designed to have a high absorption coefficient at 808 nm, the laser beam induces small-scale localized temperature oscillations at the modulation frequency. These temperature oscillations result in optical path length changes that are detected by a phase-sensitive, swept source OCT system. The OCT system uses a double-buffered Fourier domain mode locked (FDML) laser operating at a center wavelength of 1315 nm and a sweep rate of 240 kHz. High contrast is observed between phantoms containing nanoshells and phantoms without nanoshells. This technique represents a new method for detecting gold nanoparticle contrast agents with excellent signal-to-noise performance at high speeds using OCT.
Highlights
Optical coherence tomography (OCT) is a high-resolution biomedical imaging modality that produces cross-sectional and three-dimensional images of tissue microstructure by interferometrically measuring the amplitude and echo time delay of backscattered light [1]
Because the nanoshells are designed to have a high absorption coefficient at 808 nm, the laser beam induces small-scale localized temperature oscillations at the modulation frequency. These temperature oscillations result in optical path length changes that are detected by a phase-sensitive, swept source optical coherence tomography (OCT) system
We have demonstrated a new type of active contrast agent detection technique for OCT imaging
Summary
Optical coherence tomography (OCT) is a high-resolution biomedical imaging modality that produces cross-sectional and three-dimensional images of tissue microstructure by interferometrically measuring the amplitude and echo time delay of backscattered light [1]. The most utilized source of endogenous contrast is spatial variations in the scattering properties of the tissue, which produces contrast in conventional OCT images. In this case, only the amplitude of the interference signal is analyzed to form the image. Only the amplitude of the interference signal is analyzed to form the image Another source of endogenous contrast is velocity or flow. Referred to as Doppler OCT or optical Doppler tomography (ODT), these techniques analyze phase changes in the interference signal over brief time periods to detect vascular blood flow [2,3,4,5,6,7]. Non-centrosymmetric endogenous tissue components, such as collagen, can be detected using second harmonic OCT [16,17,18,19,20,21]
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